title: Rit signaling contributes to interferon-gamma-induced dendritic retraction via p38 mitogen-activated protein kinase activation.
abstract: The proinflammatory cytokine interferon-gamma (IFNgamma) alters neuronal connectivity via selective regressive effects on dendrites but the signaling pathways that mediate this effect are poorly understood. We recently demonstrated that signaling by Rit, a member of the Ras family of GTPases, modulates dendritic growth in primary cultures of sympathetic and hippocampal neurons. In this study, we investigated a role for Rit signaling in IFNgamma-induced dendritic retraction. Expression of a dominant negative Rit mutant inhibited IFNgamma-induced dendritic retraction in cultured embryonic rat sympathetic and hippocampal neurons. In pheochromacytoma cells and hippocampal neurons, IFNgamma caused rapid Rit activation as indicated by increased GTP binding to Rit. Silencing of Rit by RNA interference suppressed IFNgamma-elicited activation of p38 MAPK in pheochromacytoma cells, and pharmacological inhibition of p38 MAPK significantly attenuated the dendrite-inhibiting effects of IFNgamma in cultured sympathetic and hippocampal neurons without altering signal transducer and activator of transcription 1 activation. These observations identify Rit as a downstream target of IFNgamma and suggest that a novel IFNgamma-Rit-p38 signaling pathway contributes to dendritic retraction and may, therefore, represent a potential therapeutic target in diseases with a significant neuroinflammatory component.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, Kentucky, USA.
authors.forename: Douglas A
authors.initials: DA
authors.lastname: Andres
authors.forename: Geng-Xian
authors.initials: GX
authors.lastname: Shi
authors.forename: Donald
authors.initials: D
authors.lastname: Bruun
authors.forename: Chris
authors.initials: C
authors.lastname: Barnhart
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Lein
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D003712:Dendrites / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009154:Mutation; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D016716:PC12 Cells; D011725:Pyridines / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects; D017783:Superior Cervical Ganglion / Q000166:cytology; D013997:Time Factors; D014162:Transfection / Q000379:methods; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018631:ras Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D007093:Imidazoles; C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D011725:Pyridines; D034741:RNA, Small Interfering; D007371:Interferon-gamma; D048051:p38 Mitogen-Activated Protein Kinases; C486777:Rit protein, rat; D018631:ras Proteins; C093642:SB 203580